We plan to examine in detail the role of T lymphocytes in the afferent arm of C. parvum-induced macrophage activation. The interference of nonimmune lymphoid or other normal cell types with C. parvum activated macrophages at the effector level will also be studied. Histochemical techniques will be used to examine the cell types represented in regressing tumors, and the kinetics of tumor cells in such tumors will also be investigated. A study of the interactions between C. parvum and other agents modifying the risk of metastasis is on-going and will be pursued. BIBLIOGRAPHIC REFERENCES: Milas, L., N. Hunter, I. Basic, K. Mason, D.J. Grdina and H.R. Withers: Nonspecific immunotherapy of murine tumors with C. granulosum. J. Natl. Cancer Inst. 54: 895-902, 1975. Milas, L., T. Basic, H.D. Kogelnik and H.R. Withers: Effects of C. granulosum on the immune system of mice: Weight and histology of lymphoid organs; response to mitogens, skin allografts and a syngeneic fibrosarcoma. Cancer Res. 35: 2365-2374, 1975.